Fibroblast growth factor 21 protects the heart from angiotensin II-induced cardiac hypertrophy and dysfunction via SIRT1

Aims: This study investigated the mechanism through which fibroblast growth factor 21 (FGF21) protects against angiotensin II (Ang 11)-induced cardiac hypertrophy and dysfunction. Methods: Male silent information regulator 1 (SIRT1) fiox/flox and cardiomyocyte-specific inducible SIRT1 knockout mice (SIRT1-iK0) were generated and treated with Ang II (1.1 mg/kg/day for 4 weeks) at the age of 8-12-week-old. FGF21 treatment [2.5 mg/kg/day for 4 weeks by intraperitoneal (i.p.) injection) was initiated at the same time as the Ang II infusion. For in vitro studies, neonatal rat cardiomyocytes (NRCMs), H9c2 rat cardiomyocytes and isolated adult mouse cardiomyocytes were treated with Ang II (1 NM) and FGF21 (20 nM) for 24 h with or without SIRT1 silencing. Results: FGF21 treatment significantly attenuated Ang II-induced cardiac hypertrophy and dysfunction. SIRT1 knockout abolished the ability of FGF21 to prevent Ang 11-induced cardiac hypertrophy, fibrosis, and apoptosis, without affecting the beneficial effects of FGF21 in Ang II-induced hypertension, and did not influence the hypertension itself. FGF21 markedly increased the deacetylase activity of SIRT1 and promoted the interaction of SIRT1 with liver kinase BI (LKB1) and forkhead box protein 01 (FoxOl), resulting in decreased acetylation of these SIRT1 target proteins. Consequently, FGF21 promoted the activation of the LKB1 target adenosine monophosphate-activated protein kinase (AMPK) and altered the transcriptional activity of Fox01 on its downstream target genes catalase (Cat), MnSOD (Sod2), and Bim, resulting in reduced reactive oxygen species (ROS) accumulation and cardiomyocyte apoptosis. Conclusions: FGF21 improves cardiac function and alleviates Ang II-induced cardiac hypertrophy in a SIRT1dependent manner.